Re: Should we cacheline align PGXACT?

On Wed, Mar 1, 2017 at 5:29 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
> On 1 March 2017 at 04:50, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
>>
>> On Tue, Feb 28, 2017 at 11:44 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>>>
>>> On 28 February 2017 at 11:34, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
>>>
>>>>
>>>> So, Here are the pgbench results I got with 'reduce_pgxact_access_AtEOXact.v2.patch' on a read-write workload.
>>>
>>>
>>> Thanks for performing a test.
>>>
>>> I see a low yet noticeable performance gain across the board on that workload.
>>>
>>> That is quite surprising to see a gain on that workload. The main workload we have been discussing was the full read-only test (-S). For that case the effect should be much more noticeable based upon Andres' earlier comments.
>>>
>>> Would it be possible to re-run the test using only the -S workload? Thanks very much.
>>
>>
>> Okay, I already had the results for read-oly workload but just forgot to share it along with the results for read-write test. Here are the results for read-only
>> test,
>
>
> Thanks for conducting those comparisons.
>
> So we have variable and sometimes significant gains, with no regressions.
>
> By the shape of the results this helps in different places to the alignment patch. Do we have evidence to commit both?

Well, We have seen some regression in read-write test with pgxact
alignment patch - [1]. I may need to run the test with both the
patches to see the combined effect on performance.

[1] - https://www.postgresql.org/message-id/CAE9k0Pk%2BrCuNY%2B7O5XwVXHPuki9t8%3DM7jr4kevxw-hdkpFhS2A%40mail.gmail.com